A 7000-YEAR RECORD OF INSECT COMMUNITIES FROM A PEATLAND ENVIRONMENT,SOUTHERN QUEBEC

We present a detailed paleoentomological analysis of a 4-m pear sectio n sampled in a paludified dunefield in the St. Lawrence Lowland. Quebe c, and covering the last 7000 years. A minimum of 907 insect individua ls were recovered, representing 133 taxa (53 identified to the species level) in 26 families and 5 orders. Four insect zones were identified . Zone 1 (6800-4130 years BP) was insect-rich, including many ground b eetle species from wet and dry environments. Aquatic and rove beetles were abundant. Zone 2 (ca 3800 years BP) was very poor in insects. Thi s zone was a sand layer associated with erosion of the dune slope duri ng a short period of high water level in a beaver pond. Zone 3 (3800-3 300 years BP) contained many aquatic beetles and ante, and some bark b eetles. Zone 4 (3300 years BP to present) was mainly characterized by the abundance of rove beetles, the presence of bye introduced species in the upper (50 cm) layer of the peat section, and the abundance of t he bark beetle Polygraphus rufipennis. The study site falls within the known modem range of all but one of the identified species. In genera l, the relationship between the species composition of the vegetation and the insect communities remained obscure through the 7000-year sequ ence. However, changes in the insect communities were in agreement wit h information on their ecological requirements documented in the liter ature. The stability of the paleoentomofauna indicates that most insec ts were not influenced by the overall climatic fluctuations of the las t 7000 years.